how to fix Bessa RF focus problems (swing)

Discussion in 'Medium Format Cameras and Accessories' started by pellicle, Sep 24, 2008.

  1. pellicle

    pellicle Member

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    Hi

    I recently bought a Bessar RF to dabble in what this sort of camera can do. It has been both a revelation and a frustration. My problem is uniform focus across the image. The lens seems to swing a little to one side (probably as a result of the design that allows it to fold ;-) ) . There is some play there, but it fells much less than a degree of movement. I'm used to movements with my 4x5 camera and given that I use a 90mm lens (not unlike the 105 Skopar on the Bessar) I don't think this amount of 'free play' is enough to account for what I'm seeing.

    For example, with this image

    [​IMG]

    it seems that focus is just 'poor' at the edges, however close examination shows that its actually a tilt ofthe focal plane (camera in portrait orientation).

    Looking at the top right in more detail a pine tree quite further back which is in focus while the pine needles of "my tree" are starting to fuzz up badly.

    [​IMG]

    Looking at the middle of the focal plane the "my tree" is in focus, but the middle of that pine tree above is out of focus (consistent with the DoF created with f8).

    [​IMG]

    then looking further to the bottom its apparent that the focal plane is comming closer to the camera

    [​IMG]

    While this has some advantages in some orientations, I think I would prefer to have the focal plane at a more predictable and "normal" orientation.

    So, does anyone have any suggestions on how to fix this? I'm having trouble seeing this effect on a ground glass and loupe I made up, so this will make 'adjustment' tedious.

    Aside from that, its a nice camera!
     
  2. Anupam Basu

    Anupam Basu Member

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    Your lens shouldn't be wiggling about - certainly not enough to have mini view camera movements :smile:. Try with another lens to see if the problem is fixed.
     
  3. pellicle

    pellicle Member

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    Hi

    the bessa RF does not have interchangable lenses. Certainly with the right tools they can be removed, but I don't happen to have one spare.

    To be perhaps more clear about this camera its a Voigtlander Bessa RF which is a 120 roll film 6x9 folder.

    pardon me for not making that clearer earlier
     
  4. JPD

    JPD Member

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    I had the same problem with an Ensign Selfix 820 camera, and solved it by tightening the shutter retaining ring inside the camera.
     
  5. pellicle

    pellicle Member

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    Hi

    ok ... but the shutter / lens assembly is tight, I'm sure that its the metal base that it is mounted to. Still, I'm not sure its the 'play' that is the problem. I think its mis-aligned.
     
  6. Jim Noel

    Jim Noel Member

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    I think you are correct in assuming that the camera is out of alignment. I don't know the camera well enough to suggest a cure.
     
  7. JPD

    JPD Member

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    The lens/shutter sits very rigid in place on my RF-Bessa, with no play at all. Check the camera shutter assembly and standard carefully to find out if something is bent. On both sides of the shutter assembly there are slightly rounded metal stops that are there to hold the lens and shutter rigid.

    I hope you know what I mean. My english is limited, but better than my finnish even though we are neighbors. :tongue:
     

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  8. pellicle

    pellicle Member

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    Hi

    yep (looked at images, thanks for that) thats the spot. I can feel some free play in that whole 'plate / mount' on the end of the bellows. Perhaps a mm or maybe less. I don't think its enough to cause the alignment issue I'm seeing, but it might be.

    I have tried another method of putting the camera open on a flat and level surface and placed level across the lens (metal front rim). It is definately not level. perhaps an entire degree or maybe two.

    I bought the camera from a fellow called certo6 who is highly recommended. Certainly the camera is otherwise in perfect operational order and looks very neat for its age. Still I did pay rather a high sum for it (I consider that I paid for his time and effort in service not the camera really).


    no problems. I'm acutally a 'moved in' neighbour. I'm Australian

    :smile:

    sina ruotsilianen ja mina australialianen koska australialianen minunkin suomi on paska.
     
  9. JPD

    JPD Member

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    Can't you send it back? I thought Jürgen Kreckel had some sort of warranty on the cameras he sell.


    Ah, that explains your "-our" endings of words. :D

    Sinä oh... uh... makkara. :confused:
     
  10. pellicle

    pellicle Member

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    Hi

    I suppose I could always try, but:
    • on what grounds (it does operate well)
    • its not exactly cheap to post to and from the USA
    • I've already contacted him and he didn't think there was much to see in the images
    • one may aruge that he is not selling new cameras only refurbing them as best as possible
    • people may consider this acceptable


    such as? I don't recall typing colour and the other words are spelt the same way in both English (as used by British, Canadians and Australians) and American (as used by Americans Koreans and Japanese).

    ;-)
     
  11. JPD

    JPD Member

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    • You can probably fix it yourself. :tongue:

    You wrote "neighbour", and I wrote "neighbor" (Though I prefer brittish english. I guess I'm too affected by all the americans on the net and boards like this :tongue: )

    I hope you can solve the camera problem. The RF-Bessa is an excellent camera when it works properly. It was one of my best buys. I got mine for €40. :D
     
  12. John Koehrer

    John Koehrer Subscriber

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    1mm perhaps less is quite a bit of play in a lens standard. If it's not held perpendicular to the focusing bed it could very well be your problem. When a folder is locked down I wouldn't expect to see or feel any movement at all, at least without putting some force on the standard.
     
  13. pellicle

    pellicle Member

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    OMG, do they misspell that one too!


    :smile:

    Seriously though the Bessar RF is fantastic. I'm very interested in the new Voigtlander / Fuji folder, but I just can't see it beating this camera for 'value for money' that my Bessa RF is ... besides I prefer 6x9 (mines a real 58mm x 88mm) over 6x7 (which will probably be 56mm x 66mm)




    John ... thanks for the input that 1mm play is a significant factor. I'll now try to 'sort it out' if I can.
     
  14. John Koehrer

    John Koehrer Subscriber

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    Pellicle,
    Just shim(forward) it with a match book cover or similar to test it.
    If it tests OK then you can figure out a permanent solution
     
  15. JPD

    JPD Member

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    I fully agree. I have my 6x9 RF-Bessa with Heliar, Agfa Record II with coated Solinar and Ercona II with coated Tessar. (Plus plate cameras) I have only an enlarger for 6x7, but have made a 56 x 73mm neg holder that works well, so I don't lose so many millimeters anyway.

    It would be fun to own the "Voigtländer" Bessa III, but not sure how much I would gain in picture quality, and I don't believe the lens will be a real Heliar since it has six elements according to what I've read. Yes, I'm one of those. :rolleyes:
     
  16. pellicle

    pellicle Member

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    Hi

    I thought I'd set up a test by putting the camera on a dead level surface with the back open and then putting a level across the lens. With the back open I find that the 'sides' which form the light trap with the back door are measurably even to the film plane. Putting a level across the lens I need to pull the lens down on the outside edge to bring it level (meaning pull in from the "top" if the flop out section and focus arms is the bottom).

    I found last night that by shimming a little the the two small arms on either side of the clamp for the "front standard" (see below)

    [​IMG]

    The little 'arm' at the bottom arrow pushes against the surface on the lens standard as it closes. I put some layers of 'masking tape' on there to add some thickness and effectively push the top back more. I this seems to fix the lens alignment (and makes the entire system more rigid too)

    A quick test with a ground glass and then with a cut down sheet of film this morning confirms that focus is now pretty parallel with the film plane
     
  17. pellicle

    pellicle Member

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    you know, if you cut and past sentences and move them around enough, answer a few phone calls in the middle of your post you can make a complete muddle of what you're writing.

    reading my post above I wonder if anyone will ever make sense of that!
     
  18. pellicle

    pellicle Member

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    ohh ... and reliance on spell checkers to pick up and highlight mistakes is bad because while "cut and past" is not a spelling error its not what I wanted to say.

    sigh
     
  19. John Koehrer

    John Koehrer Subscriber

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    Pellicle,
    don't worry you'll get past it.:D
    Since you have a temporary solution in hand, now you'll have to pretty it up a bit. Tape will either wear or compress with use.
    Can you estimate the thickness of the adjustment? If you can come up with a dimension, you can replace the tape with a sliver of brass attached to the arm or the surface the arm presses against.
    Here in the US I'd get the stock from a hobby shop. You could always use a piece of tin or aluminum from a beer or soda can attached with a piece of double faced tape.
     
  20. pellicle

    pellicle Member

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    John

    yes, exactly. I have just been thinking what to use and how to attach the shim. Some heat-shrink came to mind but I am concerned that it'll also wear off soon, and I'm unsure how to attach a shim of (say) brass. I think its too thing for double sided tape, but perhaps it might be ok.

    I wonder if a thin 'bead' of silicon would do the trick?

    I can also see that there was a layer of something like 'powdercoating' or enamel on the structures which has since cracked / flaked off. I'm sure this has bee the cause of the extra play.